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See-through solar materials that can be applied to windows represent a massive source of untapped energy and could harvest as much power as bigger, bulkier rooftop solar units, scientists report in Nature Energy.

Led by engineering researchers at Michigan State University, the authors argue that widespread use of such highly transparent solar applications, together with the rooftop units, could nearly meet U.S. electricity demand and drastically reduce the use of fossil fuels."Highly transparent solar cells represent the wave of the future for new solar applications," said Richard Lunt, the Johansen Crosby Endowed Associate Professor of Chemical Engineering and Materials Science at MSU. "We analyzed their potential and show that by harvesting only invisible light, these devices can provide a similar electricity-generation potential as rooftop solar while providing additional functionality to enhance the efficiency of buildings, automobiles and mobile electronics."

Lunt and colleagues at MSU pioneered the development of a transparent luminescent solar concentrator that when placed on a window creates solar energy without disrupting the view. The thin, plastic-like material can be used on buildings, car windows, cell phones or other devices with a clear surface.

The solar-harvesting system uses organic molecules developed by Lunt and his team to absorb invisible wavelengths of sunlight. The researchers can "tune" these materials to pick up just the ultraviolet and the near-infrared wavelengths that then convert this energy into electricity.

Moving global energy consumption away from fossil fuels will require such innovative and cost-effective renewable energy technologies. Only about 1.5 percent of electricity demand in the United States and globally is produced by solar power.

But in terms of overall electricity potential, the authors note that there is an estimated 5 billion to 7 billion square meters of glass surface in the United States. And with that much glass to cover, transparent solar technologies have the potential of supplying some 40 percent of energy demand in the U.S. - about the same potential as rooftop solar units. "The complimentary deployment of both technologies," Lunt said, "could get us close to 100 percent of our demand if we also improve energy storage."

Lunt said highly transparent solar applications are recording efficiencies above 5 percent, while traditional solar panels typically are about 15 percent to 18 percent efficient. Although transparent solar technologies will never be more efficient at converting solar energy to electricity than their opaque counterparts, they can get close and offer the potential to be applied to a lot more additional surface area, he said.

Right now, transparent solar technologies are only at about a third of their realistic overall potential, Lunt added.

"That is what we are working towards," he said. "Traditional solar applications have been actively researched for over five decades, yet we have only been working on these highly transparent solar cells for about five years. Ultimately, this technology offers a promising route to inexpensive, widespread solar adoption on small and large surfaces that were previously inaccessible."

Battery Costs in Stationary Energy Could Fall by up to 66%, Grow 17-Fold by 2030

The cost of battery storage for stationary applications could fall by up to 66 per cent by 2030, according to a new report published today by the International Renewable Energy Agency (IRENA). The falling price of batteries could stimulate 17-fold growth of installed battery storage, opening up a number of new commercial and economic opportunities, the report highlights.

Launched during the ‘Innovation for Cool Earth Forum’ in Tokyo, Japan, IRENA’s Electricity Storage and Renewables: Costs and Markets to 2030 assessment of electricity storage in stationary applications also found that global storage capacity could triple if countries double the share of renewables in the energy system.

“This research demonstrates that the business case for renewable energy continues to strengthen, positioning it firmly as a low-cost and secure source of energy supply," he concluded.

The report, which is focused on stationary applications, highlights that while pumped-hydro systems currently dominate total installed power storage capacity, with 96% of the installed electricity storage power globally, economies of scale and technology breakthroughs will support the accelerated development and adoption of alternative storage technologies, such as lithium-ion (Li-ion) batteries and flow batteries.

Stationary electricity storage can directly drive rapid decarbonisation in other key segments of energy use, such as in the transport sector where the viability of battery storage for electric vehicles (EVs) is improving fast. At the end of 2016, the cost of Li-ion batteries had fallen by as much as 73 per cent for transport applications from 2010.

While Li-ion batteries in stationary applications have a higher installed cost than those used in EVs, in Germany, small-scale Li-ion battery systems have also seen their total installed costs fall by 60 per cent between the fourth quarter of 2014 and the second quarter of 2017.

“The growth of lithium-ion battery use in electric vehicles and across the transport sector over the next 10 to 15 years is an important synergy that will help drive down battery costs for stationary storage applications,” said Dolf Gielen, Director of the IRENA Innovation and Technology Centre and an author of the report. “The trend towards electrified mobility will also open up opportunities for electric vehicles to provide vehicle-to-grid services, helping feed a virtuous circle of renewable energy and storage integration.“Storage technology will deliver service flexibility to the grid and electricity storage to small-scale rooftop solar applications in markets where commercial and residential electricity rates are high, and grid feed-in remuneration is declining,” concluded Mr. Gielen.

By 2030, the calendar life of Li-ion batteries could also increase by approximately 50 per cent, while the number of full cycles possible could potentially increase by as much as 90 per cent. Other battery storage technologies also offer large cost reduction potential. High temperature “sodium sulphur” batteries could see their costs decline by up to 60%, while the total installed cost of flow batteries could potentially fall by two-thirds by 2030. Although they are subject to higher up-front costs compared to other technologies, flow batteries often exceed 10,000 full cycles, balancing the costs with very high lifetime energy throughputs.